#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
    int fib(int n)
    {
        if (n <= 2)
            return n;
        else
            return fib(n - 1) + fib(n - 2);
    }


    int main()
    {
        int n = 0;
        scanf("%d", &n);
        printf("%d\n", fib(n));
        return 0;
    }

